Purification and characterization of a sperm motility‐dynein ATPase inhibitor from boar seminal plasma

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Abstract
A sperm motility inhibitor from boar seminal plasma was purified. The purification procedure included dialysis against 0.1 M Tris‐HCl containing 0.1 mM DTT and chromatographies on SP‐Sephadex C‐25 and Phenyl‐Sepharose CL‐4B. With this procedure, the seminal plasma motility inhibitor (SPMI) preparation was highly purified with a 18% recovery of inhibitory activity. The molecular weight of SPMI in native conditions has been estimated at 50,000 by molecular sieving, but 3 polypeptides with molecular weights of 14,000, 16,000 and 18,000 were observed following polyacrylamide gel electrophoresis in denaturing conditions. SPMI is a thermolabile basic protein that is stable between pH 6 and pH 11. The observations that SPMI effects on motility of demembranated spermatozoa are reversed by Mg.ATP and that SPMI inhibited bull dynein ATPase in a concentration‐dependent manner suggest that this protein blocks the motility of demembranated spermatozoa by interfering with dynein arm function.